Only one person in 40 has an extraordinary ability to do safely what many take for granted in daily life -- talk on a cell phone while driving.

Action Points

Caution interested patients that these results reinforce the risk associated with talking on a cell phone while driving, since nearly all individuals were unable to maintain the same level of safe braking and following distance while simultaneously focusing on the phone.

Only one person in 40 has an extraordinary ability to do safely what many take for granted in daily life -- talk on a cell phone while driving.

These "supertaskers" excelled on a simulated driving exercise and a demanding, simultaneous test of memory and math skills conducted over the phone without any loss in performance on either, according to Jason M. Watson, PhD, and David L. Strayer, PhD, both of the University of Utah in Salt Lake City.

But this finding just underscores what 97.5% of their test subjects couldn't do, they wrote ahead of print in the August issue of the Psychonomic Bulletin and Review.

The vast majority became more dangerous drivers and poorer conversationalists -- despite using a hands-free headset, Watson and Strayer reported.

These findings add to a growing body of literature that suggests multitasking is usually counterproductive, Watson said in an interview.

"Generally speaking, the overwhelming majority of us engage in two things at once without expecting there to be some costs in performance," he told MedPage Today. "There is a real fundamental bottleneck in people's capacity in processing multiple things at once."

This limited capacity for attention actually constitutes one of the most robust conclusions in all of cognitive science, the researchers noted.

The more attention we devote to one task, the better we do it -- and the worse we do on others, they explained.

"Some readers may also be wondering if they too are supertaskers; however, we suggest that the odds of this are against them," the researchers cautioned in the paper.

Traffic accident rates and braking reaction and object detection times on the road bear this out, even though many "adamantly claim that they are not impaired when they use a cell phone while driving," Watson and Strayer wrote in the paper.

To see if there might be a few for whom this is actually true, they tested 200 undergraduate students using an auditory version of the operation span (OSPAN) test of executive attention, which requires memorizing items and recalling them in the correct order while concurrently performing distracting math problems.

They also performed a driving test simulating freeway driving in traffic while being monitored for braking time and distance from vehicles slowing in front of them.

Overall, participants did significantly worse when doing the two tests at the same time for brake reaction time, following distance, memory performance, and math performance (all P<0.01).

A small subset of three men and two women (2.5%) scored in the top 25% on the memory and driving tests and stayed in the top quartile on all measures without more than a standard error for the mean drop in performance when talking and driving at the same time.

The researchers noted that the "supertaskers" did not test all under the same research assistant, or in the same order of testing conditions, and their numbers were more common than suggested by chance alone.

Rather than being a statistical fluke or just more experienced at driving while talking, the researchers suggested that nature rather than nurture has given these rare individuals a genetic or biological advantage in cognitive capacity or efficiency at using those resources.

As a result, they said, "supertaskers" could provide information on the nature of cognition in multitasking. They said they intend to continue their research on these types of individuals, but their bottom line is that most of us exhibit a significant decrease in ability when we try to perform two tasks at the same time.

The researchers reported no conflicts of interest and no external funding.